1. Field of the Invention
The invention relates to novel o-aminophenolcarboxylic acids and o-aminothiophenolcarboxylic acids, which are also jointly abbreviated to o-amino(thio)phenolcarboxylic acids, and to a process for their preparation.
o-Aminophenolcarboxylic acids are needed, in particular, for the preparation of high-temperature-stable polymers, such as polybenzoxazoles (PBOs) and their precursors. Compared with the preparation of polybenzoxazoles or PBO precursors from bis-o-aminophenols and dicarboxylic acids, the use of o-aminophenolcarboxylic acids has significant advantages. For example, an o-aminophenolcarboxylic acid can be reacted with itself, i.e. a second monomer is not absolutely necessary for the polymerization. This allows purity monitoring and storage to be simplified. In addition, the stoichiometry is predefined, i.e. errors in the calculation or weighing-out of the reactants, as can occur in the reaction of bis-o-aminophenols with dicarboxylic acids, are excluded if o-aminophenolcarboxylic acids are used. Furthermore, the nature of the monomer used has a strong effect on the property profile of the PBO precursor or polybenzoxazole prepared therewith. For example, not only the thermal, electrical and mechanical behavior, but also the solubility and hydrolysis stability and numerous other properties of the polymer are greatly affected by the monomer used in the preparation.
PBO precursors in the form of a photosensitive composition can be structured inexpensively by direct methods, i.e. without an auxiliary resist. Compared with other dielectrics which can be photostructured directly, such as polyimide (PI) and benzocyclobutene (BCB), PBO precursors offer the advantage of positive structurability and aqueous-alkaline development (see EP 0 023 662 B1 and EP 0 264 678 B1). To this end, the PBO precursors used must be substantially transparent at the exposure wavelength and sufficiently soluble in the developer, which preferably contains no metal ions. Like polyimides, polybenzoxazoles also have the manor advantage that theyxe2x80x94compared with the cyclized final productxe2x80x94as readily soluble precursors, can be applied to a substrate and then cyclized, during which the solubility and thus the sensitivity to solvents and other process chemicals decreases greatly.
Besides good solubility of the precursors, advantages for the use of polybenzoxazoles in microelectronics are low moisture absorption and a good planarization capacity. Production of components using a dielectric which produces good planarization allows expensive polishing procedures (chemical mechanical polishing, CMP) to be avoided.
o-Aminophenolcarboxylic acids are disclosed, for example, in GB 811,758 and GB 1,283,476. In PBO films produced from the known monomers, the water absorption in boiling water after 24 h is 0.77%. No mention is made of the planarization behavior of the polymers produced after cyclization on the substrate or their suitability as base polymers for compositions which can be photostructured positively.
The object of the invention is to provide o-aminophenolcarboxylic acids and o-aminothiophenolcarboxylic acids which are suitable for the preparation of polymers which satisfy the greatly increased demands of microelectronics. The o-amino(thio)phenolcarboxylic acids should, in particular, enable the preparation of readily soluble polymer precursors which, after cyclization on a substrate, give polybenzoxazoles or polybenzothiazoles of low moisture absorption and high degree of planarization.
This is achieved in accordance with the invention by o-aminophenolcarboxylic acids and o-aminothiophenolcarboxylic acids of the following structure:
in which
A1 to A7 are independently of one another xe2x80x94H, CH3, OCH3, CH2CH3 or OCH2CH3;
T is O or S,; m is 0 or 1;
Z is one of the following carbocyclic or heterocyclic aromatic radicals: 
wherein Q=C-A or N,
and A=H, F, (CH2)pCH3, CF2)pCF3, O(CH2)pCH3, O(CF2)pCF3, CO,(CH2)pCH3, CO(CF2)pCF3 where p=0 to 8 (linear or branched chain, OC(CH3)3, OC(CF3)3, C6H5, C6F5, OC6H5, OC6F5, cyclopentyl, perfluorocyclopentyl, cyclohexyl or perfluorocyclohexyl,
where, in the isolated aromatic rings, a maximum of 3 nitrogen atoms may be present per ring and only 2 nitrogen atoms may be adjacent, and, in the fused ring systems, a maximum of 2 nitrogen atoms nay be present per ring,
M=a single bond, (CH3)n, (CF2)n, CH(CH3), CH(CF3), CF(CH3), CF(CF3), C(CH3)2, C(CF3)2, CH(CH6H5), CH(C6F5), CF(C6H5), CF(C6F5), C(CH3(C6H6), C(CH3) (C6F5), C(CF3) (C6H5), C(CF3) (C6F5), C(C6H5)2, C(C6F6)2, CO, SO2
with the provision that, when m=0, a 3-amino-4-hydroxyphenoxy group cannot be in the p-position to the carboxyl group.
The novel compounds have, for example, the following preferred structure: 
In compounds of this type, the ether bridges are apparently responsible for the good solubility and the good planarization properties of the polymer precursors prepared therewith. By the way, the characterization xe2x80x9cA1-A3xe2x80x9d and xe2x80x9cA4-A7xe2x80x9d in the structural formula means that the aminophenyl groups and carboxyphenyl groups contain radicals A1, A2 and A3, and A4, A5, A6 and A7 respectively.
The o-amino(thio)phenolcarboxylic acids can be prepared by
(a) reacting a halogen compound of the structure 
with a nitrophenol or nitrothiophenol (abbreviated to xe2x80x9cnitro(thio)phenolxe2x80x9d of the structure 
in the presence of at least a stoichiometric amount of a base, or with an alkali metal salt of the nitro(thio)phenol, in a solvent at a temperature between xe2x88x9210 and 80xc2x0 C., where X is a halogen atom, E is CN or COOR1, where R1=alkyl (having 1 to 5 carbon atoms), phenyl or benzyl, A1 to A7, T and Z are as defined above, and R is one of the following radicals: alkyl, alkoxyalkyl, alkenyl, alkoxyalkenyl, alkynyl or alkoxyalkynyl, each having a maximum of 6 carbon atoms, phenyl, phenacyl or benzyl, and benzylalkyl, benzylalkenyl, benzyloxyalkyl, benzyloxyalkenyl, benzylalkoxyalkyl or benzylalkoxyalkenyl, each having a maximum of 4 aliphatic carbon atoms; and
(b) reducing and hydrolyzing the resultant nitro compound to the amino compound, and removing the group R.
In this synthesis, which is very economical, a halogen-containing ester or a corresponding nitrile is thus reacted with a nitro(thio)phenol having an R-protected hydroxyl or mercapto group in the opposition to the nitro group. The nitro compound formed is then reduced to the corresponding amino compound, the ester or nitrile group is hydrolyzed to the carboxyl group, and the protecting group R is removed
Alternatively, the o-amino(thio)phenolcarboxylic acids can also be prepared by
(a) reacting a nitro compound of the structure 
with a phenol or thiophenol (abbreviated to (thio)phenol) of the structure 
in the presence of at least a stoichiometric amount of a base, or with an alkali metal salt of the (thio)phenol, in a solvent at a temperature between xe2x88x9210 and 80xc2x0 C.,
where X is a halogen atom, E is CN or COOR1, where R1=alkyl (having 1 to 5 carbon atoms) , phenyl or benzyl, A1 to A7, T and Z are as defined above, and R is one of the above mentioned radicals; and
(b) reducing and hydrolyzing the resultant nitro compound to the amino compound, and removing the group R.
In this preparation process, which is likewise very economical, a halogen-containing nitro compound having a protected hydroxyl or mercapto group in the o-position to the nitro group is thus reacted with a (thio)phenol containing an ester or nitrile group. The nitro compound formed is thenxe2x80x94in the manner indicated abovexe2x80x94subjected to a reduction, hydrolysis and removal of protecting group.
The preparation of nitro(thio)phenols containing a protected hydroxyl or mercapto group in the o-position to the nitro group has been described in the parallel German patent application Ser. No. 197 42 135.0 xe2x80x9co-Nitro(thio)phenol derivatives, and their preparationxe2x80x9d (docket GR 97 P 3683).